Field of the Invention
The invention relates to a pressure-sensitive adhesive layer for a transparent conductive film having a patterned transparent conductive thin film and to a transparent conductive film with pressure-sensitive adhesive layer. The invention also relates to a transparent conductive laminate produced using the transparent conductive film with pressure-sensitive adhesive layer. The transparent conductive film with pressure-sensitive adhesive layer or the transparent conductive laminate may be subjected to a processing treatment as needed and then used to form a transparent electrode for a display such as a liquid crystal display or an electroluminescence display or a touch panel such as an optical, ultrasonic, capacitance, or resistive touch panel. Particularly, the transparent conductive film with pressure-sensitive adhesive layer of the invention is suitable for use as an electrode substrate of an input device in a capacitive touch panel.
Description of the Related Art
A conventionally known transparent conductive film includes a transparent film substrate and a transparent conductive thin film (such as an ITO film) placed on the substrate. When used, such a transparent conductive film also forms a transparent conductive film with pressure-sensitive adhesive layer, which has a pressure-sensitive adhesive layer provided, for bonding to other members, on the film substrate of the transparent conductive film on the side where the transparent conductive thin film is not provided.
The transparent conductive thin film is patterned when the transparent conductive film or the transparent conductive film with pressure-sensitive adhesive layer is used as an electrode substrate for a capacitive touch panel (JP-A-2009-076432). The transparent conductive film with pressure-sensitive adhesive layer having such a patterned transparent conductive thin film is used together with any other transparent conductive film or the like to form a laminate, which is advantageously used for a multi-touch input device that can be operated with two or more fingers at the same time.
Unfortunately, by the patterning of the transparent conductive thin film, a step is formed in the transparent conductive thin film so that a clear difference is made between the patterned and non-patterned parts to degrade the appearance. Specifically, the presence and absence of the pattern clearly appears to degrade the appearance when external light from the viewer side is reflected from the transparent conductive thin film or when internal light from the display device side is transmitted through the transparent conductive thin film.
Thus, there is proposed a transparent conductive film in which an anchor coat layer composed of high-refractive-index and low-refractive-index layers is interposed between a substrate and a transparent conductive thin film formed thereon, and the thickness of each anchor coat layer is adjusted, so that the pattern of the transparent conductive thin film is made less visible (JP-A-2010-015861). There is also proposed a transparent conductive film in which a light transmittance-reducing layer such as a colored layer is placed on a transparent conductive film so that the pattern of a transparent conductive thin film is made less visible (JP-A-2010-027391). There is also a study in which the pattern of a transparent conductive thin film is made less visible by reducing the difference in light transmittance or reflectance between the patterned and non-patterned parts of the transparent conductive thin film.